1. Field of the Invention
This invention relates to the tracking of liquid flow in pipelines and more particularly it concerns novel methods and apparatus for ascertaining the presence and direction of flow of water in an in-service gas pipeline.
2. Description of the Related Art
The present invention is particularly useful in the maintenance of gas pipeline supply systems through which combustible gas is delivered to a public utility or from the public utility to its customers.
When floods and water main breaks occur, water may infiltrate into nearby gas distribution piping through cracks or joints in the piping where the pressure of the water is higher than that inside the piping. The presence of water does not in itself cause a problem; but when the infiltration becomes excessive, the water may severely restrict the flow of the gas or even create a complete blockage of gas flow. In order to ascertain the location along the pipeline where infiltration is occurring, it is important not only to be able to detect the presence of water along the pipeline, it is also important to ascertain its direction and flow at a particular location. It is also important, during the operation of detecting the presence and flow of water in a pipeline, not to interrupt the normal flow of gas through the piping.
Prior attempts to detect the flow of water in a gas pipeline have had limited success. Such prior attempts have involved drilling an opening in the wall of the gas pipe and attaching telescope or viewing tube to the opening. A lens was provided within the tube near the opening so that gas would not escape up through the viewing tube. In order to see the water flow inside the gas pipe, lights, such as flashlights were attached to the outer surface of the viewing tube; and fiber optic lines extended from the flashlights down inside the gas pipe to light up its interior. This technique gave poor results because the interface between the flashlights and the fiber optic lines resulted in much of the light being reflected away from the gas pipe. Also, when the water in the pipeline flowed slowly, it was very difficult to ascertain its direction of flow or that it was flowing at all.
The following patents disclose various arrangements for detecting moisture and contaminants in fluids and for detecting leaks in pipes and vessels.
U.S. Pat. No. 3,585,963 discloses a device for detecting the presence of moisture in fluid flowing in a pipe. According to this patent, the fluid contacts a moisture indicating element which is visible through a window in the pipe and which changes color in response to the moisture.
U.S. Pat. No. 5,509,375 discloses a device for detecting the presence of contaminants in fluid being applied to a workpiece. According to this patent, the fluid is supplied through a transparent tube within which an optical fiber extends. The optical fiber illuminates the contaminants which can be viewed through the tube wall.
Japanese Patent No. 57-196129 (A) discloses a means for detecting leaks through a suspected leakage site in a pipeline. An inflatable bag, which is coated on the outside with a material which changes color on contact with water, is positioned at the site and is inflated to press the material against the suspected leakage site. Then, if water is leaking through this site, it will contact the material and change color so that it can be seen when it emerges through the leak.
U.S. Pat. No. 4,921,374 discloses an arrangement for preventing groundwater from leaking into a sewer pipe. According to this arrangement, a water-swellable material which contains a dye is positioned at a suspected leakage point above a sewer line. Water which infiltrates into the line becomes colored by the dye and can be detected downstream of the suspected leakage point.
U.S. Pat. No. 5,167,867 discloses a method of detecting leaks in a pipeline by injecting an odorant into the pipeline and checking for odors downstream of the injection point.
U.S. Pat. No. 5,574,213 discloses an arrangement for testing a vessel for pressure leaks. The arrangement comprises the injection of a fluorescent dye to a fluid being charged into the vessel under pressure. An illumination means illuminates the outside of the vessel and causes any dye which leaks through the vessel wall to fluoresce.
U.S. Pat. No. 4,566,313 discloses an arrangement for detecting the location of a leak in a vessel such as a swimming pool. According to this arrangement, a dye is injected into the pool near a suspected leakage site and the movement of the dye toward the leak is observed.
U.S. Pat. No. 4,580,442 discloses an arrangement for locating air leaks from a fire sprinkling system. According to this arrangement, the normally air filled portion of the system is filled with an aqueous solution of an efficient wetting agent and a water soluble dye. Then, pressure is applied to the system to force the dye through any leaking portions of the sprinkler system.
U.S. Pat. No. 5,043,141 discloses an injection system for forcing a liquid which exhibits chemiluminescent or bioluminescent properties into an observation chamber.
Russian Patent SU-807-098 discloses an arrangement for detecting leaks from an object. The object is filled with an air-ozone mixture and is placed into a transparent sealed chamber which is filled with ethylene. If the air-ozone mixture leaks out from the object, it will react with the ethylene to produce a chemiluminescent effect such as a visible glow.